This can be a diminutive of William (meaning “resolute protection”) or, for girls, Willa (meaning the same, since it’s derived from William) or Willow (like the tree). It’s also a word meaning determination, like when your little Will’s “iron will” makes car seat buckling a battle.
Will is pretty hard to shorten. But you could use Willie.
Famous people named Will:
Actors Will Smith, Will Rogers, Will Ferrell, Will Arnett, Will Forte, and Will Geer; novelist Will Self; songwriter Will Jennings; drummer Will Champion; football player Will Allen.
In the popular 2018 movie Dumplin', the main character is Willowdean Dickson - called Will by her friends.